1. Field of the Invention
The present invention generally relates to equipment used in the maintenance and servicing of oil and gas production wells, and more particularly, relates to power jaws or wrenches of the type used in conjunction with making or breaking threaded joints between successive tubing elements that make-up the continuous tubing string extending through a well bore into the underground deposits.
2. Related Art
In the construction of oil or gas wells, it is usually necessary to construct long drill pipes. Due to the length of these pipes, sections of pipe are progressively added to the pipe string as it is lowered into the well from a drilling platform. It is common practice to use wrench assemblies to apply a predetermined torque to make-up or break out the drill pipe connections. The wrench assemblies are typically located on a platform, either on rails or hung from a derrick on a chain. Examples of prior art wrench assemblies are described in U.S. Pat. Nos. 5,060,542; 5,386,746 and 5,868,045 all issued to inventor Thomas D. Hauk. The text of all three U.S. Pat. Nos. 5,060,542, 5,386,746 and 5,868,045 are incorporated by reference in their entirety into this application.
To make-up or break out a threaded pipe connection, the wrench assemblies of the prior art general include the use of an active (or wrenching) jaw device that supplies torque to the section of pipe above or below the threaded connection, while a passive (or back up) jaw device supplies a reaction torque below or above the threaded connection, respectively, depending upon whether the pipe connection is being made-up or broken out. Particularly, the prior art wrench assemblies described in U.S. Pat. Nos. 5,060,542; 5,386,746 and 5,868,045 disclose the use of three levels of jaws, where the jaws at each level are of a type that energize when turned in a predetermined direction so as to have a stronger grip on the pipe when turned in such direction. The jaws on the top and bottom levels are oriented so as to turn the pipe in one direction, while the jaw on the middle level is oriented to turn the pipe in the opposite direction. The upper, middle and lower jaws are positioned in vertically spaced relationship and connected together in a self-contained tool or wrench assembly. The upper and lower jaws are fixed to a common frame, whereas the middle jaw is pivotally connected between the upper and lower jaws on the common frame.
To form a pipe joint, the top pipe section is rotated (spun up), as by a spinning tool, until only final tightening is required. Then, the wrench assembly is adjusted such that the upper jaw engages a section of the pipe just above the pipe joint. The middle jaw then engages the section of the pipe just below the pipe joint. The lower jaw is positioned below the tool joint, being then adjacent to the pipe itself, but does not engage the pipe when the joint is being made-up. The upper and middle jaws are then closed on the pipe, following which the upper jaw set is rotated to make the joint. Thereafter, the upper and middle jaw sets are opened so as to release the tightened pipe joint.
To break (or loosen) a joint prior to unthreading, as by spinning out by use of a conventional spinning tool, the wrench assembly is moved vertically such that the middle jaw engages the pipe assembly just above the joint and the lower jaw engages the pipe assembly just below the lower joint. When loosening a joint, the upper jaw is usually positioned above the joint but is not in engagement with the pipe assembly. The middle and lower jaws are then closed on the pipe assembly above and below the joint respectively. The middle jaw is then rotated counterclockwise to break or loosen the joint.
In summary, making of a pipe joint is accomplished by locking the middle jaws on the bottom portion of a pipe joint, and employing the top and middle jaws to turn the top portion of the pipe joint clockwise. Breaking of a joint is accomplished by locking the bottom jaws on the bottom pipe joint portion, and employing the middle and bottom levels of jaws to rotate the top portion of the pipe joint counterclockwise.
The jaws of the current wrench assemblies are capable of adapting to receive pipes of various diameters. As described in the referenced patents, each jaw includes a hook having a shank end extending from the hook. The shank end is threaded. A head is also provided that is adapted to receive the shank end of the hook. A nut assembly is provided at the end of the head opposite the hook for threadedly engaging the shank end of the hook. The nut includes handles that facilitate the manually turning of the nut in either direction to open and close the hook end of the jaw to receive pipes of varying diameters. The relationship between the nut, hook and head are such that the rotation of the nut causes the jaw to open or close to a desired position relative to the particular diameter of the pipe joint.
To make-up or break out a drill pipe connection, high torque must be supplied over a large angle which is supplied through energizing the jaws. The jaws are initially energized by providing fluid-operated grip cylinders that pivot the hook and head relative to one another, closing and thereby tighten the grip the jaw has on the pipes. The initial engagement of the pipe by the grip cylinders commences the torquing, which allows subsequent torquing to be more effective. Other fluid-operated means, such as a hydraulic torque cylinder, are then provided to effect the torquing.
As explained above, while the prior art jaws include automated mechanisms for gripping the pipe and for applying high torque to the jaws, the prior art jaws still require manual adjustment of the wrenches to allow for the receipt of pipes of varying diameter. As such, to commence the making and breaking process, each jaw has to be manually opened and closed to allow the wrenches to receive pipes of varying diameter. Requiring manually operation of the jaws increases the operational time associated with the make-up and break out process and also increase the risk of injury by operator contact with the wrench assembly.
A need therefore exists for an improved jaw and jaw assemblies that reduce the time it takes to make-up or break out a tubular connection. A further need exists for increasing safety of operation of the jaws by minimizing operator contact.